This invention relates to a spring clip for holding a carrier of a friction pad in a disc brake for a vehicle. The spring clip has a base with an arm extending therefrom that is brought into engagement with a rotor after the friction pad has been worn to a predetermined thickness to create a noise and alert an operator that continued use of the friction pad may impair optimum braking.
In disc brakes, it is common to provide wear warning structure to indicate that a friction pad has worn to a thickness wherein continued use may impair the optimum braking capability of a brake system. The wear warning structure is most often a defined by a cantilever spring that is associated with the backing plate of the friction pad such as disclosed in U.S. Pat. No. 4,745,992 and 5,687,817 or in combination with an anti-rattle spring as disclosed in U.S. Pat. No. 5,388,670. While such wear warning structure functions in an adequate manner, it does involve additional processing as the cantilever spring is fixed to the backing plate during the manufacture of the friction pad.
In the manufacture of a pad spring, it was observed that a substantial quantity of scrap material is produced during a stamping process. During the stamping process, material is progressively removed from a substantially rectangular sheet until a final shape is produced that is designed to hold a friction pad from rattling. The final shape, defined by first and second legs that are joined together by a spacer, is designed to cover the rail to provide a smooth and oxidation free surface on which an ear on a backing plate slides during a brake application. The amount of material designated as scrap in the manufacture is essentially equal to a dimension between the first and second legs less the spacer width which is at least equal to the width of a rotor and a running tolerance between the rotor and the surface of the friction pads. In accordance with the present invention, a portion of the material previously considered as scrap and in particular the material originally located between a base for the first and second legs is retained during the stamping process and shaped to define first and second cantilever arms. The first and second cantilever arms form wear indicators by being engaged, after a predetermined wear of the friction pads, by ears that extend from backing plates for the first and second friction pads. Thereafter, the cantilever arms are moved into engagement with the rotor to create a noise or sound and thereby inform an operator of a wear thickness of a friction pad that could impair braking through the continued use of the friction pads in a disc brake.
A primary object of the present invention is to provide a disc bake with a wear indicator which is an integral component of a spring clip, the spring clip being secured to an anchor to provide a sliding surface on which a backing plate of a friction [slides] during a brake application.
According to this invention, the spring clip holds an ear that extends from backing plate for a friction pad in an alignment rail of an anchor for a disc brake. The spring clip provides a sliding surface for a projection or ear during a brake application. During a brake application, an actuation force is applied to the backing plate to move the friction pad toward and into engagement with a rotor. The spring clip is characterized by first and second legs that are separated by a spacer. The first and second legs have a surface that substantially matches and covers the rail of the anchor of the disc brake. Each leg has at least one tab that extends from the base and engages the anchor to fix the position of the base and correspondingly the first and second legs with respect to the anchor and a cantilever arm. The cantilever arm extends inwardly in plane substantially perpendicular to the base of at least one of the legs and has a lip located that is located in a plane substantially parallel with the rail. The cantilever arm is located on the spring clip such that after the friction pad has worn to a predetermined thickness, the projection or ear on the backing plate engages the cantilever arm. Thereafter, whenever an actuation force that is applied to the backing plate moves the friction pad into engagement with the rotor during a brake application, the lip is also brought into engagement with the rotor. The lip on engagement with the rotor causes the cantilever arm to vibrate and create an audible sound to alert an operator that optimum braking may thereafter be impaired through the continued use of this friction pad in the disc brake. According to the invention, a plurality of cantilever arms may also be provided on a spring clip to provide an indication of tapered wear that can occur in a disc brake.
An advantage of this invention resides in the use of a spring clip that provides a sliding surface for movement of a backing plate for a friction pad with a cantilever arm that is sequentially moved by an ear on the backing plate, after a predetermined amount of wear has reduced the thickness of the friction pad, into engagement with a rotor to create a sound that is used to inform an operator of a wear condition of the friction pad.
FIG. 1 is schematic illustration of a disc brake having a spring clip made according to the principals of the present invention;

FIG. 2 is a sectional view of the disc brake of FIG. 1 taken along lines 2xe2x80x942;
FIG. 3 is a perspective illustration of a portion of the friction pad, backing plate, spring clip, rotor, and rail on the anchor of the disc brake of FIG. 1;
FIG. 4 is a schematic illustration of the perspective illustration of FIG. 3 when the friction pad has a first thickness;
FIG. 5 is a schematic illustration of the perspective illustration of FIG. 3 when the friction pad has been worn to a second thickness;
FIG. 6 illustrates a stamping processing for a spring clip of the type used in the disc brake of FIG. 1;
FIG. 7 is a perspective illustration of the spring clip of FIG. 6.